1.Field of the Invention
The present invention relates to a drawer-type cooking device, which can be provided with a manual operation assisting mechanism and a method for controlling opening and closing of a door thereof.
2.Description of the Related Art
In the related art, there has been proposed a cooking device comprising an apparatus body having a heating chamber in which an object to be heated is housed, a door for shielding the heating chamber from outside, a bottom plate moving in conjunction with the door, a sliding mechanism for sliding the bottom plate, a motor for driving the bottom plate, transmission means for transmitting a drive force of the motor to the bottom plate, a latch device for closing and retaining the door, a door open/close switch, and a control circuit for controlling drive of the motor so as to operate the door upon reception of a signal from the door open/close switch (Japanese Patent Laid-Open Publication No. 3-45820 (Patent Document 1)). The bottom plate is directly coupled to the lower portion of the door in the vicinity of the lower hem. When the door is opened, the sides of the bottom plate are in an open state.
Also, there has been proposed a cooking device in which a slide body in which an object to be heated is housed is slidably provided in a cooking device body, comprising detecting means for detecting that the slide body has been slid out, control means for outputting an excitation command signal when receiving a detection signal from the detecting means, and an electromagnet leg portion disposed on the bottom face of the cooking device body and excited when receiving the excitation command signal (Japanese Patent Laid-Open Publication No. 6-109257 (Patent Document 2)). When the slide body is slid out, the excitation command signal is output from the control means based on detection by the detecting means, and the electromagnet leg portion disposed on the bottom face of the cooking device body is excited. The electromagnet leg portion is chucked to a metallic placing face to prevent the cooking device from being turned over, so as to use the cooking device in a stable state all the time
Also, there has been proposed a microwave oven, wherein a heating container having an opening in its top is provided so as to be freely drawn out from a body housing, a heating chamber for confining microwave is formed by the heating container and a lid portion provided in the body housing side and covering the opening of the heating container, and electromagnetic wave leakage is prevented by providing a choke groove between an opening peripheral portion of the heating container and the lid portion facing the opening peripheral portion, so as to eliminate the electromagnetic wave leakage even if a food placing portion has a movable drawer structure (Japanese Patent Laid-open Publication No. 11-237053 (Patent Document 3)).
There has been proposed a cooking device in which a placing portion of an object to be heated of a heating chamber has a drawable structure, comprising a cooking device body having a heating chamber, a drawer body movably disposed in the cooking device body such that the drawer body can be drawn out from the heating chamber of the cooking device body to the outside, and a slide rail for moving the drawer body in the cooking device body, wherein the slide rail is disposed outside of the heating chamber, so that it is not necessary to form the sliding mechanism with parts or a material having high heat resistance and flame resistance and it is possible to prevent the occurrence of faulty discharge by microwave (Japanese Patent Laid-Open Publication No. 2005-221081 (Patent Document 4)).
There has been proposed a drawer-type cooking device, wherein a drawer body having a door and a heating container in which an object to be heated is placed therein is disposed in a cooking device body in which a heating chamber using microwave is formed therein, in a movable manner between a housed position where the heating container is housed in the heating chamber, and a drawn-out position where the heating container is drawn out from the heating chamber to the outside, and a sliding mechanism allowing the drawer body to be moved is constituted by right and left slide rails outside of the heating chamber and a center slide rail in which a drive mechanism is disposed, the respective slide rails and the drive mechanism being disposed isolatedly from the heating chamber, so that the slide rails and the drive mechanism are not exposed to a high temperature and microwave or are not affected by food debris which could cause a breakdown (Japanese Patent Laid-Open Publication No. 2006-38296 (Patent Document 5)). Also, there has been disclosed a drawer-type food warmer having a moving rail only on the bottom face and in which the right and left side faces are opened (U.S. Pat. No. 6,849,835B2 (Patent Document 6)).
The inventions described in the above respective documents seem to have following points to be improved concerning supporting of the door. That is, in the inventions disclosed in Japanese Patent Laid-Open Publication No. 3-45820,Japanese Patent Laid-Open Publication No. 6-109257,Japanese Patent Laid-Open Publication No. 11-237053 (Patent Documents 1 to 3), the lower side portion of the door is only butt against the bottom plate to be fixed thereto. Thus, in the case where the door is heavily loaded by body weight, a heated object or the like, an fixed portion of the door and the bottom plate could be deformed. If the fixed portion is deformed, there is a possibility that microwave for heating leak from a gap generated between the inclined door and the body to the outsider and it is necessary to pay enough caution when the load is put on the door.
In the Japanese Patent Laid-Open Publication No. 2005-221081 (Patent Document 4), the moving mechanism is provided in right and left side walls outside of the heating chamber, and an angle for fixing the moving mechanism is attached to the door. Therefore, a force acting on the door is supported by the cooking device body by being relatively dispersed via the moving mechanism provided in the right and left and the center of the lower portion. Even when the drawer body is drawn out, the door is not inclined forward and is stably supported by the cooking device body. However, in Japanese Patent Laid-Open Publication No. 2005-221081 (Patent Document 4), the moving mechanism disposed in the right and left side wall faces extend through the right and left sides of the heating container when the drawer body is drawn out. Thus, when an object to be heated, for example, a heavy object such as a pot with soup therein or the like is put into or removed from the heating container which is combined with the door, the moving mechanism stands in the way, and the usability is low. Furthermore, from the standpoint of appearance, the visual quality needs to be improved. Also, Japanese Patent Laid-Open Publication No. 2006-38296 (Patent Document 5), in which the moving mechanism for supporting the door of the drawer body is disposed at three places of right and left side wall faces and a bottom wall face outside of the heating chamber, has the similar points to be improved as those of Japanese Patent Laid-Open Publication No. 2005-221081 (Patent Document 4). Furthermore, although U.S. Pat. No. 6,849,835B2 (Patent Document 6) has such a similar point being provided with a drawer structure, however discloses not the cooking device, but an electric warming device, in which the drawer is only manually operated and does not have an electric moving mechanism. The electric warming device does not have an electromagnetic wave sealing mechanism or a latch hook as a safety mechanism since it is not a microwave oven. Since the drawer does not have the electric mechanism, a moving mechanism simply by a lower rail is employed.
FIG. 10 is a perspective view of a drawer-type cooking device having a conventional structure. FIG. 11 is a side view of the drawer-type cooking device shown in FIG. 10. A cooking device body 1 has a heating chamber 3 for cooking an object to be heated. A drawer body 2 is movably, namely, slidably disposed in the cooking device body 1 such that the drawer body 2 can be drawn out from the heating chamber 3 of the cooking device body 1 to the front side. The cooking device comprises a movable rail 8 formed of an angle member as a moving mechanism 4 for slidingly moving the drawer body 2 in the cooking device body 1. The drawer body 2 comprises a door 6 for opening and closing the heating chamber 3 and a heating container 7 for placing and housing an object to be heated. The heating container 7 has side walls in the right and left sides, a back wall in the back side disposed in the heating chamber 3 of the cooking device body 1, and an opening in the top, and the door 6 is fixed to the front thereof. When the door 6 closes an opening of the heating chamber 3, the internal space of the heating chamber 3 becomes a sealed space by internal wall faces of the cooking device body 1 and the drawer body 2, so as to prevent microwave from leaking.
The door 6 of the drawer body 2 is supported by the cooking device body 1 by right and left side wall faces located outside of the heating chamber 3 via the moving mechanism 4. The moving mechanism 4 comprises a fixed rail 9 and the movable rail 8 sliding along the fixed rail 9. The fixed rail 9 is attached to the right and left wall faces of the heating chamber 3 outside of the heating chamber 3 of the cooking device body 1. The movable rail 8 is attached to an internal side wall face of the door 6 via a fitting 10 so as to extend from the internal side wall face of the door 6 of the drawer body 2 to the inside of the heating chamber 3 of the cooking device body 1. Since the moving mechanism 4 for moving the drawer body 2 in the cooking device body 1 is disposed outside of the heating chamber 3, it is not necessary to use expensive parts or material having high heat resistance and flame resistance for the movable rail 8 and the fixed rail 9 which constitute the moving mechanism 4. Also, since the moving mechanism 4 is disposed outside of the heating chamber 3, a risk of discharge by microwave is eliminated without being affected by microwave emitted in the heating chamber 3. In order to drive the moving mechanism 4, a DC motor is disposed as a drive mechanism. A transmission mechanism such as a gear is coupled to a rotation output shaft of the DC motor, and a pinion positioned in the last stage of the transmission mechanism meshes and engages with a rack attached to the movable rail 8.
In the known drawer-type cooking device having an automatic opening and closing door driven by a motor, it is indispensable to detect and determine a door position in order to control opening and closing of the door. Since the rotation direction of the motor cannot be determined only by a single rotation pulse from the motor, it is necessary to use a sensor or a switch for detecting an absolute position. In the drawer-type cooking device, opening and closing control in a door position close to a fully closed position or a fully opened position is considered to be important, and a detection switch for detecting the door position is provided in a position close to the fully closed position or the fully opened position. A moving distance of the door can be obtained by accumulating the single rotation pulse from the motor.
However, in the case where a door opening/closing operation is manually performed in a place other than where the detection switch is provided, similar rotation pulses are obtained in the opening operation and the closing operation based on the single rotation pulse when the motor is manually rotated. Thus, if the door is stopped in a position where the detection switch is not provided, a microcomputer cannot determine whether the door is manually operated in the opening direction or the closing direction when a subsequent opening/closing operation is manually performed. As a result, even if a manual operation assisting mechanism is employed, a door opening/closing operation by assisting the manual operation cannot be performed in an intermediate stop position other than the fully opened position and the fully closed position. In order to detect the door position in the intermediate stop position other than the fully opened position and the fully closed position, it is necessary to dispose a plurality of position detecting switches in the intermediate stop position.
The present applicant has already filed a patent application concerning a drawer-type cooking device having a manual operation assisting function of detecting a manual opening/closing operation by a user and controlling rotation of a motor according to the opening/closing direction to assist the opening/closing operation by a user (Japanese Patent Application No. 2006-308976). The drawer-type cooking device achieves the manual operation assisting function, and detects the motor rotation direction by an optical sensor and a light generating element.
In relation to the door position, there has been proposed a power slide door device for vehicles, wherein first and second square-wave pulses having different phases are generated in response to actuation of a slide door which is opened and closed by drive means, four time interval data are detected in parallel from time interval data of rising pulse edges and falling pulse edges of the respective first and second square-wave pulses, and the drive means is controlled on the basis of the four time interval data with high accuracy obtained in one cycle, so as to safely actuate the slide door (Japanese Patent Laid-Open Publication No. 2005-76319 (Patent Document 7)).
When the speed of electrically opening and closing the drawer body 2 (FIG. 10 and FIG. 11) is controlled, the speed is determined by a duty ratio of a rectangular wave voltage supplied to the DC motor. If a control device malfunctions by breakdown or short circuit in the motor wiring such that the duty ratio of the rectangular wave output from the control device is set to the maximum, there is a risk that the opening/closing operation is performed at a maximum speed when it is not expected by a user. Conventionally, such a structure that a malfunction does not occur unless a plurality of failures occur at the same time is employed by using failure mode and effects analysis (FMEA). Also, it has been confirmed that, even if the malfunction occurs, the speed does not reach a dangerous door opening/closing speed from the relationship of the performance of the mounted DC motor, the structure of the drive mechanism and load weight. Therefore, a malfunction countermeasure is not particularly taken.
The automatic door opening and closing function of the drawer-type cooking device needs to be operated by a relatively high torque since the drawer body is moved with a heavy object of several kilograms placed thereon. Thus, an impact by collision at the time of the door opening/closing operation is great. As a function of reducing the impact, speed restriction is provided as disclosed in Japanese Patent Laid-Open Publication No. 2006-38300 (Patent Document 8). However, a motor malfunction cannot be handled, and there is a possibility that the automatic door opening and closing function runs out of control to possibly perform a high speed operation.
Accordingly, in opening/closing a door of a drawer-type cooking device having a manual operation assisting mechanism, there is such a problem to be solved, to detect at least an opening/closing direction of a door by a manual opening/closing operation by a user, and preferably, the opening/closing direction and an absolute position of the door, or furthermore, to detect the opening/closing direction of the door or the absolute position of the door in addition to the opening/closing direction with respect to the opening/closing operation by a user so as to control to perform an appropriate electrically-assisted opening/closing operation.
An object of the present invention is to provide a method for controlling opening and closing of a door for a drawer-type cooking device, in which at least the opening/closing direction of the door by the manual opening/closing operation by a user, and preferably, the absolute position of the door in addition to the opening/closing direction of the door are detected even when the door is in a door-open state in a position other than the fully opened position and the fully closed position, and a drawer-type cooking device allowing the subsequent appropriate electrically-assisted automatic opening/closing operation of the door, and allowing to reduce the number of parts such as a position sensor.
In the field of microwave oven, new distinct configuration of automatic drawer type is emerging of late, for which this invention is intended for a further improvement.
This invention is to enhance safety measures in the automatic drawer operation against electromagnetic or mechanical disturbance as well as component malfunction, in order to improve assurance of operation.